In disc drives, there is a need to maintain a fly height spacing between a disc and an air bearing surface of a head in a desired range. When the disc is flat and there is no externally applied shock, then the aerodynamic force generated at the air bearing surface and a preload force combine to provide the desired fly height spacing. When the disc drive is subjected to shock, however, then the disc can be deflected so that the fly height spacing changes, and the head can also be deflected so that the fly height spacing changes. If the deflections of the disc and the head are slow enough and small enough, then the naturally stabilizing interaction of the aerodynamic force and the preload force can maintain the fly height spacing in a desired range. If the deflections are too large or too fast, then the fly height spacing will exceed the desired range and the disc drive will malfunction. The problem is compounded by the fact that the preload force is transferred to the disc and tends to cause a small deflection of the disc under the head. Closed loop electronic fly height control systems are known, however, in some cases the shock is too large or too fast for adequate compensation by a fly height control system. Methods and apparatus are needed to improve the control of fly height, particularly in small form-factor disc drives.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.